Improved thermal insulation design practices on ships' structural boundaries

Since their early development, the construction and outfitting of steel vessels have presented a unique challenge to the insulation designer in ensuring comfort and quality insulation treatments. The drive to make large commercial and military sea-going vessels lighter, faster, and stronger invariably contributes to complexities of stiffening members, compartmentalization, and system integration. In so doing, the designer must first balance the cost of thermal insulation treatments against several competing factors: the capacity of heating and cooling equipment, the cost of this equipment, and the cost of energy to meet thermal requirements. In the past, the US shipbuilding industry has relied on a fixed table of maximum allowable thermal transmittance values, or "U" values, to determine the thickness of insulation for particular configurations. In this paper, the authors show that these "U" values are inadequate, in comparison to current standards for the use of thermal insulation on walls and envelopes in building construction, and that a selective increase in insulation thicknesses used on ships can reduce the weight of fuel and equipment for space heating and cooling. The authors also propose that the insulation designer be encouraged to incorporate different methods of estimating heat flows given specific environmental conditions and stiffener configurations compared with long-held industry standards. These methods include computer-assisted Finite Element Analysis, recognition of varying extreme conditions, and actual stiffener configurations that contribute to thermal flows. With these changes, the insulation systems for US built ships could be improved thermally, the total ship weight could be reduced, and the insulation systems could be installed more quickly, thereby reducing the cost of construction.